The invention relates to a heat exchanger, in particular, for use in automobile manufacture, comprised of extruded profile sections, preferably of aluminum or aluminum alloy, which are arranged parallel to one another and are connected with their two ends to a manifold, respectively, wherein between neighboring sides of two profiled pipe sections a lamellar arrangement is attached by soldering. The multi-chamber profiled pipes can be coated with zinc, brazing, and/or a flux agent in order to improve the corrosion resistance and soldering properties (compare DE 195 15 909 A1).
In particular, the invention relates to heat exchangers which are soldered with non-corrosive flux agents according to the inert gas soldering method.
However, it was found that by unevenness and roughness, in particular, longitudinal grooves in the extrusion direction of the extruded profiles, the soldering agent does not remain at the locations provided therefor but will move away from the actual soldering location, for example, by capillary action or by grooves so that during soldering a destruction or damage by means of a so-called soldering erosion occurs. By soldering erosion the properties, such as seal-tightness, bursting pressure resistance, pressure change resistance, and corrosion resistance, required for the prescribed use of the heat exchanger can be changed disadvantageously. Soldering erosion can neither be safely prevented nor detected with the conventional process safety methods.
It is therefore an object of the invention to provide first a heat exchanger of the aforementioned kind in which a secure soldering connection is present without there being the risk that a part of the soldering agent can flow from the manifold to the lamella arrangement, or that damage to or destruction of the profiled pipe occurs. Moreover, the heat exchanger should be producible in a simple and cost-saving way.
This is achieved according to the invention in that between the manifold and the lamella arrangement at the outer side of the profiled pipe at least one obstruction, positioned transversely to the longitudinal direction of the pipe, is provided for preventing the flow of the soldering agent, for example, AlSi solder or AlZn solder, wherein by means of this obstruction the grooves extending in the longitudinal direction of the pipe profile are significantly reduced in their depth and/or are interrupted. By means of the obstruction, a soldering agent flow away from the actual soldering location is significantly reduced. The prescribed connection between the manifold, the profiled pipe, and the lamella arrangement is provided. By means of the obstruction, a safe means is provided in a simple way without great extra expenditure for reducing the soldering erosion.
In a special embodiment of the invention, the obstruction is formed as a smoothing zone of the profiled pipe. In this connection, the smoothing zone has a depth which is approximately 5-100 xcexcm and preferably is not greater than 15% of the profiled pipe wall thickness. This smoothing zone prevents that the soldering agent flows by capillary action from the manifold to the lamella.
In a special embodiment of the invention, the obstruction is an embossment so that by means of a simple embossing action a portion transverse to the profile can already become practically groove-free. It is beneficial when the embossment is provided on both sides of the flat profiled pipe having a minimal curvature. A protection is obtained on both sides.
The invention also relates to a method for producing a heat exchanger, wherein extruded profiled pipe sections are attached on two manifolds, wherein between neighboring profiled pipe sections lamellar arrangements are connected by soldering.
However, it is also an object of the invention to design a method such that during soldering a safe connection can be obtained; at the same time, the method should be performable in a simple and cost-saving way; a groove-induced soldering erosion is to be prevented.
According to the invention this object is solved in that, before separating or cutting to length a strand, the profiled pipe sections are provided with at least one obstruction for interrupting the flow of the soldering agent. Such extruded flat profiled pipe sections then enable the safe construction of a heat exchangers.
It is beneficial when the obstruction is generated by an embossment which reduces the roughness of the profiled pipe because the method can be easily carried out in this way.
It is recommended in this connection to provide embossment tools on two oppositely positioned sides of the flat profiled pipe which produce the embossment simultaneously. This ensures that practically in a single working step the obstruction is produced around the profiled pipe; at the same time, by applying the embossment action on both sides, such a weak pressure is generated in the pipe that no or only minimal bending or deformation of the pipe is to be expected. According to a special embodiment of the invention, before cutting the sections, the embossment actions are performed on both sides of the cutting line on the profiled pipe. By the simultaneous embossment action on both sides of the cutting line, it is achieved that the one end of the profiled pipe section is provided with an obstruction while the adjacent profiled pipe section has at its leading end an embossment; again this method can be performed easily and cost-savingly.
In order to obtained a sufficient obstruction for the soldering agent as a function of the thickness of the pipe, the width and the depth of the embossment on the extruded profiled pipe can be adjustable as desired so that it is always ensured that a safe smoothing of the embossed pipe is realized.
By the configuration of the embossment tools and the embossment process, it is ensured that there is no disadvantageous effect on the properties for the prescribed use (seal-tightness, bursting pressure resistance, pressure change resistance, and corrosion resistance).